high CVSS 8.1 EPSS 0.27%

CVE-2026-64440·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: staging: rtl8723bs: fix OOB write in HT_caps_handler() HT_caps_handler() iterates pIE->length bytes and writes into HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct HT_caps_element). Because pIE->length is a raw u8 from an over-the-air 802.11 AssocResponse frame and is never validated, a malicious AP can set it up to 255, causing up to 229 bytes of out-of-bounds writes into adjacent fields of struct mlme_ext_info. Truncate the iteration count to the size of HT_caps.u.HT_cap using umin() so that data from a longer-than-expected IE is silently ignored rather than written out of bounds, preserving interoperability with APs that pad the element. An early return on oversized IEs was considered but rejected: it would bypass the pmlmeinfo->HT_caps_enable = 1 assignment that precedes the loop, silently disabling HT mode for APs that append extra bytes to the HT Capabilities IE.

Severity
high
Software
Kernel
Fixed in
7.1.4
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.27% — higher than 17% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-64440 scores 8.1 on CVSS, so a successful attack would be serious — but at 0.27%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.19

Until: 7.1.4

Fixed in: 7.1.4

How to fix this CVE

Update your Linux kernel to version 7.1.4 or later to fix an out-of-bounds memory write vulnerability in the RTL8723BS wireless driver's HT capabilities handler. This flaw allows a malicious WiFi access point to corrupt kernel memory by sending oversized 802.11 association response frames. Prioritize this update if your system uses RTL8723BS WiFi adapters or if you operate in untrusted wireless environments.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version with: uname -r — vulnerable versions are 6.19 through 7.1.3
  2. Verify RTL8723BS driver presence with: lsmod | grep rtl8723bs — if loaded, the vulnerable code path is active
  3. Monitor system logs for memory corruption signs: sudo dmesg | grep -i 'segfault\|oops\|memory' — malicious APs may trigger kernel panics
  4. After updating, confirm patch with: uname -r — should show 7.1.4 or later, then reboot and verify: grep rtl8723bs /boot/config-$(uname -r) to confirm driver is enabled

FAQ

What is CVE-2026-64440?

A kernel vulnerability in the RTL8723BS WiFi driver that fails to validate frame length fields from 802.11 association responses. An attacker controlling a rogue WiFi access point can exploit this to write up to 229 bytes beyond a fixed 26-byte buffer, corrupting adjacent kernel memory structures.

Is CVE-2026-64440 being actively exploited?

No — this vulnerability is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, the low barrier to exploitation (requiring only a malicious AP in wireless range) warrants prompt patching.

What versions of Kernel are affected by CVE-2026-64440?

Linux kernel versions 6.19 through 7.1.3 are vulnerable. Version 7.1.4 and later contain the fix. Distributions based on older kernel versions (e.g., RHEL 8, Ubuntu 22.04) may not be affected if they ship earlier kernel branches.

How do I check if my server is vulnerable to CVE-2026-64440?

Run uname -r and lsmod | grep rtl8723bs — if your kernel is between 6.19–7.1.3 AND the rtl8723bs module is present, your system is vulnerable.

Does Defensia detect CVE-2026-64440?

Yes — Defensia's CVE advisory scanner compares installed kernel version against known vulnerable ranges. If kernel 6.19–7.1.3 is detected on a monitored server with RTL8723BS driver enabled, CVE-2026-64440 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-53384CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails dw8250_probe() registers the 8250 port via serial8250_register_8250_port() and then, if the device has a clock, registers a clock notifier. If clk_notifier_register() fails, probe returns the error but leaves the 8250 port registered. The matching serial8250_unregister_port() lives in dw8250_remove(), which is not called when probe fails, so the port slot stays occupied until the device is rebound or the system is rebooted. The devm-allocated driver data is freed while the port still references it (via the saved private_data and serial_in/serial_out callbacks), so any access to that port slot before a rebind is a use-after-free hazard. Unregister the port on the clk_notifier_register() error path.
CVE-2026-52931CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: batman-adv: tp_meter: avoid use of uninit sender vars batadv_tp_recv_ack() and batadv_tp_stop() are only valid for tp_vars in the BATADV_TP_SENDER role. When called with a BATADV_TP_RECEIVER role, it proceeds to read sender-only members that were never initialized, leading to undefined behavior. This can be triggered when a node that is currently acting as a receiver in an ongoing tp_meter session receives a malicious ACK packet. Guard against this by checking tp_vars->role immediately after the lookup and bailing out if it is not BATADV_TP_SENDER, before any of those members are accessed.
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References

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